The American Civil Liberties Union of Ohio and the New York-based public advocacy group Demos sued Republican Secretary of State Jon Husted in April, claiming the state illegally drops registered voters from its registration list based on their failure to vote in recent elections.

The 6th U.S. Circuit Court of Appeals in Cincinnati found Ohio’s process violates federal law. One judge on the court’s three-judge panel concurred in part, and dissented in part.

The decision sends the case back to the lower court, which must establish a process for either restoring purged voters to the rolls or allowing them to vote provisionally and having all those votes count.

In a statement, Husted said he awaits a “workable remedy” from the district court.

“To that end, if the final resolution requires us to reinstate voting eligibility to individuals who have died or moved out of Ohio, we will appeal,” he said.

The ACLU’s Mike Brickner said time is of the essence, with the general election less than seven weeks away and early voting beginning even sooner.

“It’s important that we have some finality here, so that poll workers, voters and election officials all know what the rules are in advance of Election Day,” he said.

It wasn’t clear exactly how many voters have been affected by the purge process, but estimates are tens to hundreds of thousands.

Voters can check their registration online. The state’s deadline to register, re-register or update an address is Oct. 11.

Husted says the appeals court ruling overturns 20 years of practice carried out by the last four elections chiefs.

The state’s attorneys had argued that other states “use processes like, or more expansive than, Ohio’s.” In an appeals court in a brief, they noted methods in Indiana, Missouri, Tennessee and Montana.

The 6th Circuit sided with the groups’ allegations that the state’s maintenance of the voter rolls “has led to, and threatens to continue to result in, the disenfranchisement of eligible Ohio voters.”

Judge Eugene E. Siler Jr., wrote in a separate opinion that he finds Ohio’s procedure lawful, noting the state’s removal process includes other factors such as failure to respond to address-confirmation notices.

The groups’ lawsuit had claimed that Husted “has cancelled the registrations of voters in part because of their failure to respond to a notice mailed to their registered address, including notices sent to homeless voters who frequently cannot receive mail reliably.”

Last year in Democrat-leaning Cuyahoga County, home to Cleveland, about 40,000 individuals were illegally purged from voter rolls for choosing not to vote, with a disproportionate number from poor and minority neighborhoods, according to the Ohio chapter of the A. Philip Randolph Institute, a labor group representing minorities.

A federal judge rejected the groups’ complaint in June after finding their claims lacked merit.

The Justice Department had urged the appeals court to reverse the district judge’s decision.

In a July brief, the department said federal law requires a voter’s removal when the voter becomes ineligible because of a change of residence, but only after the state confirms the move.